Imidazolinyl benzoic acids, esters and salts, methods for the preparation thereof and use of such compounds as herbicidal agents is described in U.S. Pat. Nos. 4,188,487, 4,297,128 and 4,554,013. The patented compounds are effective for the selective control of a wide variety of undesirable monocotyledonous and dicotyledonous weed species in the presence of cereal crops such as barley, wheat and rye and have been used effectively in this manner in most wheat and barley producing countries around the world. Among the most effective of these compounds is an isomeric mixture of two positional isomers, namely, 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester. In graminaceous crops such as wheat, barley and rye, this isomeric mixture has provided excellent control of many important grasses and broadleaf weeds including: wild oats (Avena spp.), wind grass (Apera spicaventi), black grass (Alopecurus myosuroides), wild mustard (Brassica kaber), wild buckwheat (Polygonum convolvulus), field pennycress (Thlaspi arvense) and wild radish (Raphanus raphanistrum). However, as the use of the imidazolinyl benzoic acid esters has increased and spread to grain producing countries all around the world, it has become increasingly evident that the limited solubility of the above-said esters in aqueous solutions restricts the concentrations of ester obtainable in such solutions and hence their use in aqueous sprays. Thus, it was that Paserala et al U.S. Pat. No. 4,871,388 issued Oct. 2, 1989, devised a formulation which provided a water dispersible liquid concentrate of the ester containing 0.2 to 1 molar equivalents of polybasic acid and a water miscible organic solvent. In this formulation the imidazolinyl benzoic acid ester is dissolved in the water miscible solvent and remains in solution when the concentrate is diluted with water for spray application. Although this formulation is highly effective and extensively used it is not entirely satisfactory since crystalization of the ester may occur under adverse temperature conditions and the use of organic solvent is sometimes considered objectionable.
As viewed today, organic solvents are recognized as having a potential deletarious effect upon the environment. Moreover, the use of organic solvents in the preparation of pesticide formulations can be hazardous to workmen in the formulation and packaging plants and, likewise, to the farmer who is exposed to the formulations during pesticide application if the handling of such formulations is not adequately controlled. Additionally, it is well recognized that use of organic solvents in the preparation of pesticide formulations generally increases the cost of the product, both in manufacture and shipping of the finished formulation.
It would, therefore, be most advantageous if the imidazolinyl benzoic acid esters of this invention could be formulated in a manner which would be (1) free of organic solvents, (2) readily dispersed in water for application to the foliage of plants and soil and (3) exhibit enhanced biological activity over an equivalent amount of the ester suspension concentrate formulation applied alone.